Viriobenthos in aquatic sediments: variability in abundance and production and impact on the C-cycle

In the last 15 years viruses have been acknowledged as important components of the benthic microbial community, but our understanding of their role in the functioning of aquatic systems remains poor. Viruses can affect bacterial assemblages and mineralization activities, but the extent of their influence remains unclear. We synthesised available data on viriobenthos dynamics to understand which factors drive the variability in their abundance and production and to quantify their influence on the benthic carbon cycle. Results highlighted a large variability in viral abundance (from 2 × 10⁸ to 7 × 10⁹ virus ml^?1) and production estimates (from 1 × 10⁷ to 5 × 10⁸ virus ml^?1 h^?1) obtained with different techniques. This variability limits the comparability of data across studies and indicates the need to improve protocols and develop standard methods. The dynamics of viruses infecting prokaryotes appeared linked to prokaryotic metabolism, supporting the hypothesis that benthic viruses originate directly in the sediment as a result of infection events rather than sinking from the water column. Sediment characteristics (porosity, temperature, depth) appeared to effect viral production, mostly indirectly by influencing bacterial productivity and abundance, but possibly also interfering with the rate of virus–host encounter. Conversely, trophic status appeared unrelated to viral parameters. Viral contribution to carbon turnover appeared low and unrelated to temperature, water depth, trophic status and salinity. More detailed studies are needed to understand the pelagic contribution to the viriobenthos and the extent to which dissolved organic carbon released by viruses is effectively used by bacteria.     

Effects of the middle Holocene high sea-level stand and climate on Amazonian mangroves

The high sea-level stand during the mid-Holocene is a benchmark in mangrove dynamics along the north-east/south-east coast of Brazil and provides a reference point for landward and seaward mangrove migrations corresponding to changes in relative sea level (RSL). However, evidence of the impacts associated with RSL fall on the northern Brazilian coast is scarce. Multi-proxy data from the highest tidal flats of the Bragança Peninsula in northern Brazil revealed modern herbaceous areas were occupied by mangroves Rhizophora and Avicennia from ~6250 to ~5850 cal a bp , and only Avicennia between ~5850 and ~5000 cal a bp . The same tidal flats were vegetation-free between ~5000 and ~4300 cal a bp . A combination of a high sea-level stand (0.6 ± 0.1 m) at ~5000 cal a bp and a dry early–middle Holocene in the Amazon probably caused an increase in porewater salinity of tidal flats, which resulted in a mangrove succession from Rhizophora to Avicennia dominance. RSL fall accentuated this process, contributing to mangrove degradation between ~5000 and ~4300 cal a bp . RSL fall, and a wetter period over the past ~4300 cal a bp caused a mangrove migration from highest to lowest flats, followed by expansion of herbaceous vegetation on the highest flats.     

Water level as the main driver of the alternation between a free-floating plant and a phytoplankton dominated state: a long-term study in a floodplain lake

This 10-year field data study explores the relevance of water level fluctuations in driving the shift from a free-floating plant (FFP) to a phytoplankton dominated state in a shallow floodplain lake from the Lower Paraná River. The multi-year natural flood pulse pattern in the Lower Paraná River drove the ecosystem regime from a FFP-dominant state during very high waters (1998–1999) to absolute phytoplankton prevalence with blooms of nitrogen fixing Cyanobacteria during extreme low waters (2008–2009). Satellite images support the observed changes over the decade and show the decrease of the surface lake area covered by FFP as well as the modification of the spectral firm in open waters, which documents the significant increases in phytoplankton chlorophyll a concentrations. We discuss the possibility that, despite a slow eutrophication in these highly vegetated systems, water level changes and not nutrients account for the shift from a floating macrophyte community to phytoplankton dominance. Cyclic shifts may occur in response to the seasonal floodpulse, but more strongly, as indicated by our results, in association to the extreme drought and flood events related to the El Niño Southern Oscillation, which is linked to discharge anomalies in the Paraná River.     

Ensemble projections for wine production in the Douro Valley of Portugal

Wine production is largely governed by atmospheric conditions, such as air temperature and precipitation, together with soil management and viticultural/enological practices. Therefore, anthropogenic climate change is likely to have important impacts on the winemaking sector worldwide. An important winemaking region is the Portuguese Douro Valley, which is known by its world-famous Port Wine. The identification of robust relationships between atmospheric factors and wine parameters is of great relevance for the region. A multivariate linear regression analysis of a long wine production series (1932–2010) reveals that high rainfall and cool temperatures during budburst, shoot and inflorescence development (February-March) and warm temperatures during flowering and berry development (May) are generally favourable to high production. The probabilities of occurrence of three production categories (low, normal and high) are also modelled using multinomial logistic regression. Results show that both statistical models are valuable tools for predicting the production in a given year with a lead time of 3–4 months prior to harvest. These statistical models are applied to an ensemble of 16 regional climate model experiments following the SRES A1B scenario to estimate possible future changes. Wine production is projected to increase by about 10 % by the end of the 21^st century, while the occurrence of high production years is expected to increase from 25 % to over 60 %. Nevertheless, further model development will be needed to include other aspects that may shape production in the future. In particular, the rising heat stress and/or changes in ripening conditions could limit the projected production increase in future decades.     

Remarks on sequence stratigraphy and taphonomy of the Malvinokaffric shelly fauna during the KAČÁK Event in the Apucarana Sub-basin (Paraná Basin), Brazil

The Eifelian–Givetian (Middle Devonian) transition constituted an important paleoenvironmental event for the Malvinokaffric Realm in the Apucarana Sub-basin (Paraná Basin). This study highlights integration between taphonomy and sequence stratigraphy, and four depositional sequences are identified during the transition. In Sequence 1, the presence of a typical normal-sized Malvinokaffric fauna is recorded. In the transgressive systems tract (TST) of Sequence 2, no benthic fossils are present, and this is interpreted as a stratigraphic marker of an event of significant paleoenvironmental change (KA?ÁK Event). In Sequence 3, the TST has abundant bioclasts, which become rarer toward the top of the section, i.e., within the transgressive systems tract. The original habitat of this autochthonous to parautochthonous fauna was a low-energy environment between the fair weather wave base and the storm wave base of the Devonian epicontinental sea. In the highstand systems tract of this sequence, the presence of normal-sized Pennaia paulianna and lingulids demonstrates the return of more ambient conditions. Sequence 4 is of Carboniferous age. Its limit is a second-order sequence boundary recording a lowstand systems tract formed by a fluvial depositional system. The low diversity and the disappearance of taxa are not the result of a taphonomic bias, but reflect the post-KA?ÁK Event.     

Terrestrial photogrammetry without ground control points

Terrestrial photogrammetry should be the survey technique of choice when updating large scale urban maps and GIS databases, where 3D data and attribute data are required. Its main drawback is the need for Ground Control Points (GCP) to reference the survey. To make image georeferencing easier and to provide control information, the use of a simple system, made of a photogrammetric camera fastened to a GPS antenna, is proposed. A photogrammetric block, composed by at least three images, is taken around the object with the receiver measuring in kinematic mode. Tie points are automatically extracted by Structure from Motion (SfM) algorithms or measured manually; block orientation is performed by GPS assisted Aerial Triangulation. Advantages as well as limitations of the system are discussed, with particular attention to GPS availability or ill-conditioned block configurations. The issue of system calibration (i.e. measurement of eccentricity between camera and antenna) is also addressed. Several test cases are presented, in which absolute accuracies, verified on check points independently surveyed range from 4 to 7 cm.     

Estuarine flooding in urban areas: enhancing vulnerability assessment

The assessment of vulnerability provides valuable knowledge in the risk assessment steps of a risk governance process. Given the multiscale, multilevel, and multisectorial aspects of flood risk, the diversified entities that directly and indirectly intervene in risk management require specific outputs from the assessment studies. Urban areas in estuarine margins are particularly exposed and vulnerable to flooding. Such interface conditions are found in the Old City Centre of the Seixal, located in the Tagus estuary, Portugal. Here, two distinct methodologies were applied for the assessment of territorial vulnerability. A regional, lower-scale, methodology explores the application of the statistical procedure based on the SoVI^® at the statistical block level. A second, local and higher-scale, methodology is based in data collected through field matrices at the building and statistical sub-block level. Comparison of results revealed that the lower-scale assessment provides information on the vulnerability drivers at the regional and municipal level. Nevertheless, only at a higher-scale, it is possible to characterize and differentiate the smaller geographical units of analysis that compose the Old City Centre of Seixal. The lower-scale vulnerability assessment allows a strategic response, based on adaptation measures such as spatial planning, institutional capacity building and public awareness. The local level assessment provides more accurate knowledge to support local emergency planning and the allocation of operational and material resources at the urban level. Nevertheless, rather than antagonistic, both models can be considered as complementary, having in mind the requirements of an holistic flood risk governance model.

     

Estimating greenhouse gas emissions from cattle raising in Brazil

The study estimated, for the first time, the greenhouse gas emissions associated with cattle raising in Brazil, focusing on the period from 2003 to 2008 and the three principal sources: 1) portion of deforestation resulting in pasture establishment and subsequent burning of felled vegetation; 2) pasture burning; and 3) bovine enteric fermentation. Deforestation for pasture establishment was only considered for the Amazon and Cerrado. Emissions from pasture burning and enteric fermentation were accounted for the entire country. The consolidated emissions estimate lies between approximately 813 Mt CO₂eq in 2008 (smallest value) and approximately 1,090 Mt CO₂eq in 2003 (greatest value). The total emissions associated with Amazon cattle ranching ranged from 499 to 775 Mt CO₂eq, that of the Cerrado from 229 to 231 Mt CO₂eq, and that of the rest of the country between 84 and 87 Mt CO₂eq. The full set of emissions originating from cattle raising is responsible for approximately half of all Brazilian emissions (estimated to be approximately 1,055 Mt CO₂eq in 2005), even without considering cattle related sources not explicitly estimated in this study, such as energy use for transport and refrigeration along the beef and derivatives supply chain. The potential for reduction of greenhouse gas emissions offered by the Brazilian cattle industry is very high and might constitute Brazil’s most important opportunity for emissions mitigation. The study offers a series of policy recommendations for mitigation that can be implemented by public and private administrators at a low cost relative to other greenhouse gas reduction options.     

Continuing current in multiple channel cloud-to-ground lightning

In this study we analyze the effects of continuing current initiated by strokes following a new channel to ground in multiple stroke flashes using high-speed video records, electric field measurements from a fast antenna and lightning detection network data. We observed that the long continuing current initiated by a stroke that follows a new channel also obeys the pattern in the initiation of long continuing current suggested by Rakov and Uman [Rakov, V.A., Uman, M.A., 2003. Lightning: Physics and Effects, 687pp., Cambridge Univ. Press, New York.]. We also verify that the statement of Rakov and Uman [Rakov, V.A. and Uman, M.A., 1990. Some properties of negative cloud-to-ground lightning flashes versus stroke order, Journal of Geophysical Research. 95, 5447–5453.] reporting that: “...strokes initiating long continuing currents tend to have lower initial electric field peak than regular strokes” is valid for strokes that create a new channel to ground and are followed by long continuing current (CC). Apparently the reduction of peak current value (I_p) when the stroke is followed by a long CC is stronger than the I_p increase that is commonly observed when strokes follow a new channel. We also find that the “exclusion zone” proposed by Saba et al. [Saba, M.M.F., Pinto, O. Jr., Ballarotti, M.G., 2006a. Relation between lightning return stroke peak current and following continuing current, Geophysical Research Letters 33, L23807, doi:10.1029/2006GL027455.] is valid for new channels initiating CC, and finally we verify that a number of strokes in the same channel larger than four or the existence of a long CC current do not always consolidate the channel in a multiple stroke flash.